Role of Reflexes from the Heart in the Control of the Circulation under Stressful Conditions.
Progress rept. 1 Sep 72-31 Aug 73,
UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF PHYSIOLOGY
Pagination or Media Count:
Studies show that maneuvers which increase and decrease atrial activity are associated with an increase in heart rate. Further, the elevation of cardiac rate was associated with a decrease in efferent vagal activity. It is now clear that an increase in activity from the atria produces an increase in heart rate while a decrease in heart rate occurs when carotid sinus activity is increased. The finding that an increase in heart rate is associated with both an increase and decrease in atrial firing seems to be an anomaly. The best explanation for the increase in heart rate with hemorrhage is that other receptors are involved. That these receptors might be of ventricular origin is currently being investigated. Severe hypothensive hemorrhage was carried out in three subjects while monitoring efferent vagal activity. A marked elevation of vagal efferent activity occurred at very low blood pressure levels which may confirm the existence of a vagovagal reflex mechanism that might lead to episodes of syncope. Modified author abstract
- Anatomy and Physiology